Micromechanisms Involved in Grain Boundary Engineering

2005 ◽  
Vol 495-497 ◽  
pp. 1225-1230
Author(s):  
Andre Luiz Pinto ◽  
Carlos Sergio da Costa Viana ◽  
Luiz Henrique de Almeida
Keyword(s):  
Grain Boundary ◽  
Electron Backscatter Diffraction ◽  
Boundary Migration ◽  
Coincidence Site Lattice ◽  
Inconel 625 ◽  
Grain Boundary Engineering ◽  
Inconel 600 ◽  
Special Boundaries ◽  
Deformation Step ◽  
Backscatter Diffraction

Grain boundary engineering has been applied to different materials in order to increase properties particularly sensitive to intergranular phenomena. This work analyses the micromechanisms that allow the control of the amount of special boundaries which respect coincidence site lattice theory. α-brass, a lead alloy, Inconel 625 and Inconel 600 were submitted to different thermomechanical treatments and were analyzed via electron backscatter diffraction in order to characterize their grain boundaries. The occurrence of thin twins in some crystal directions during the deformation step seems to determine the results obtained as well as strain induced boundary migration.

Grain Boundary Engineering: Progress and Challenges

2007 ◽  
Vol 539-543 ◽  
pp. 3389-3394 ◽  
Author(s):  
Wei Guo Wang
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Electron Backscatter Diffraction ◽  
Coincidence Site Lattice ◽  
Grain Boundary Character Distribution ◽  
Grain Boundary Engineering ◽  
Special Boundaries ◽  
Grain Boundary Character ◽  
Proposed Model ◽  
Backscatter Diffraction

The progress of grain boundary engineering (GBE) is overviewed and the challenges for further investigations emphasized. It points out that, the electron backscatter diffraction (EBSD) reconstruction of grain boundaries, which gives the information of connectivity interruption of general high angle boundaries (HABs), is more significant than purely pursuing high frequency of so-called special boundaries. The criterion for the optimization of grain boundary character distribution (GBCD) needs to be established. The energy spectrum and the degradation susceptibility of grain boundaries of various characters including HABs and low Σ（Σ≤29） coincidence site lattice (CSL) needs to be studied and ascertained. And finally, the newly proposed model of non-coherent Σ3 interactions for GBCD optimization are discussed.

Towards Optimization of Grain-Boundary Structures in Annealed Nickel

1996 ◽  
Vol 54 ◽  
pp. 356-357
Author(s):  
C.B. Thomson ◽  
V. Randle
Keyword(s):  
Grain Boundary ◽  
Electron Backscatter Diffraction ◽  
Coincidence Site Lattice ◽  
Annealing Twin ◽  
Average Deviation ◽  
Special Boundaries ◽  
Boundary Rotation ◽  
Twin Formation ◽  
Backscatter Diffraction ◽  
Statistical Preference

Many properties of materials are influenced by intergranular structure. Increasing the number of grain boundaries with favourable properties, or ‘special’, boundaries, can enhance the performance of a material in service. However, the criteria that must be satisfied for a boundary to be classified as special are not widely understood. For example, it has been shown that Σ3 coincidence site lattice (CSL) boundaries alone present a resistance to corrosion greater than for other boundary types in nickel (fee). In contrast, Rolim Lopes et al. observed no statistical preference for Σ3s in the grain boundary network of FeAl (bcc), and Bouchet and Priester discovered that in nickel there was a weak propensity for segregation to several boundary types, including Σ3, Σ1 1 and Σl9a CSLs.Commercially pure and superpure nickel specimens have been subjected to the strain annealing treatments detailed in the Table. Fig. 1 shows the results from an electron backscatter diffraction study of the commercial purity specimens (CI to C4). It is clear that the only boundary types that increase in frequency with increased thermal processing are Σ3n (n=l,2,3) CSLs. An abundance of annealing twins was observed for sample C4, and is unique to this sample, and this accounts for the very high proportions of Σ3s. Samples CI to C3 were annealed under vacuum, whereas C4 was treated in air, and it is proposed that the dominant energy minimization mechanism has changed from grain/grain boundary rotation for samples CI to C3, to annealing twin formation for sample C4. If the structure of a grain boundary evolves towards the exact misorientation of what is considered a special CSL type, the special properties of that boundary will, in general, become more marked. Σ3s have been shown to possess special properties. Fig. 2 shows the average deviation from exact misorientation for the Σ3s in each sample, normalised by the Brandon criterion for maximum permitted deviation. This clearly indicates that the Σ3s created by annealing twin formation can be considered more special than those produced via grain/grain boundary rotations.

Application of Electron Backscatter Diffraction to Grain Boundaries

2010 ◽  
Vol 160 ◽  
pp. 39-46 ◽  
Author(s):  
Valerie Randle
Keyword(s):  
Grain Boundary ◽  
Electron Backscatter Diffraction ◽  
Experimental Methodology ◽  
Polycrystalline Materials ◽  
Grain Boundary Engineering ◽  
Network Characteristics ◽  
Grain Boundary Plane ◽  
Electron Backscatter ◽  
Measurement Strategies ◽  
Backscatter Diffraction

The technique of electron backscatter diffraction (EBSD) is ideal for the characterisation of grain boundary networks in polycrystalline materials. In recent years the experimental methodology has evolved to meet the needs of the research community. For example, the capabilities of EBSD have been instrumental in driving forward the topic of ‘grain boundary engineering’. In this paper the current capabilities of EBSD for grain boundary characterisation will be reviewed and illustrated by examples. Topics are measurement strategies based on misorientation statistics, determination of grain boundary plane distributions and grain boundary network characteristics.

Grain Boundary Migration in Alumina

2000 ◽  
Vol 652 ◽  
Author(s):  
Jeffrey K. Farrer ◽  
N. Ravishankar ◽  
Joseph R. Michael ◽  
C. Barry Carter
Keyword(s):  
Grain Boundary ◽  
Small Angle ◽  
Electron Backscatter Diffraction ◽  
Boundary Migration ◽  
Liquid Films ◽  
Grain Boundary Migration ◽  
Sintering Process ◽  
Orientation Relationships ◽  
Electron Backscatter ◽  
Backscatter Diffraction

ABSTRACTThe sintering process of ceramics involves grain-boundary migration (GBM) that is accompanied by mass transport across an interface. In this study, electron backscatter diffraction (EBSD) has been used to examine grain-boundary migration in alumina bicrystals with liquid films at the interface. EBSD patterns, taken near the sintered interface, have been used to study the effects of crystallography on GBM and to study the orientation relationships within the migrated regions of the crystal. Results indicate that the direction of migration is not always the same as that predicted by the current theories on GBM. It was also found that there may be small-angle misorientations in the migrated regions.

Grain Boundary Self-Diffusion in Nickel

2007 ◽  
Vol 263 ◽  
pp. 207-212 ◽  
Author(s):  
Vĕra Rothová ◽  
Jiří Buršík ◽  
Milan Svoboda ◽  
Jiří Čermák
Keyword(s):  
Grain Boundary ◽  
Grain Orientation ◽  
Electron Backscatter Diffraction ◽  
Coincidence Site Lattice ◽  
Self Diffusion ◽  
Electron Backscatter ◽  
Cold Rolled ◽  
Backscatter Diffraction ◽  
Arrhenius Temperature ◽  
Diffusion Profiles

Grain boundary self-diffusion in both the cast and the cold-rolled Puratronic 4N5 nickel was studied in the temperature range from 600 °C to 1000 °C. The experiments were carried out with the samples pre-annealed at 1100 °C in comparison to the samples pre-annealed at intended individual diffusion temperatures. The relative grain orientation was analyzed on the same samples by means of electron backscatter diffraction (EBSD) and grain boundaries (GBs) were characterized in terms of the coincidence site lattice (CSL) model. Considering the non-linear Arrhenius temperature dependencies obtained for most specimens by using conventional method of profile evaluation in the B-type kinetics and the appearance of two high-diffusivity paths in diffusion profiles measured, a more suitable BB-type and AB-type diffusion models were applied for data evaluation.

Morphology Evolution of Grain Boundary Carbides in Highly Twinned Inconel Alloy 600

2016 ◽  
Vol 879 ◽  
pp. 1111-1116 ◽  
Author(s):  
Hui Li ◽  
Jiao Rong Ma ◽  
Xin Rong Liu ◽  
Shuang Xia ◽  
Wen Qing Liu ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Aging Time ◽  
Electron Backscatter Diffraction ◽  
Coincidence Site Lattice ◽  
Morphology Evolution ◽  
Alloy 600 ◽  
Inconel Alloy ◽  
Electron Backscatter ◽  
Backscatter Diffraction

The effects of grain boundary characters on the morphology evolution of grain boundary carbides in Inconel Alloy 600 with high proportional low Σ coincidence site lattice (CSL) boundaries aged at 715 oC for 1-100 h were investigated by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). During the aging process, the carbides precipitated at coherent twin (Σ3) boundaries are very few and finest within all the aging time. Bar like carbides precipitated near both sides of the incoherent twin (Σ3) boundaries, and bigger carbides than that of coherent Σ3 boundaries had been found on the incoherent Σ3 boundaries. Bar like carbides precipitated near only one side of Σ9 boundaries, and much bigger carbides than that of Σ3 boundaries have been found on the Σ9 boundaries. The morphology of carbides precipitated at Σ27 and random grain boundaries are similar, and is bigger than that of precipitated at other grain boundaries. The carbides precipitated at grain boundaries with all types grow bigger with the aging time prolonging, but their growth rates are different.

scholarly journals Texture and Shape Analysis of Quartzite Mylonites of the Metamorphic Sole of the Samail Ophiolite (Oman): Evidence for Syn- and Post-Obduction Deformation

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 111
Author(s):  
Peter Hallas ◽  
Wilfried Bauer
Keyword(s):  
Grain Boundary ◽  
Electron Backscatter Diffraction ◽  
Boundary Migration ◽  
Arabian Plate ◽  
Grain Boundary Migration ◽  
Main Role ◽  
Subgrain Rotation ◽  
Shear Sense ◽  
Subduction System ◽  
Backscatter Diffraction

The metamorphic sole, tectonically welded to the base of the Samail ophiolite in a supra-subduction system, is assumed to play the main role in strain accumulation during later thrusting onto the Arabian Plate (i.e., during obduction). The present study deals with five quartzite samples representative of the upper amphibolite and lower greenschist facies parts of the sole. Whole-rock textures obtained by neutron time-of-flight technique were coupled with microstructural observation using electron backscatter diffraction analyses. The quartz microstructural fabrics and textures in the upper and lower parts of the sole represent grain boundary migration and [c]-in-Y textures and subgrain rotation recrystallization and {r}-in-Z textures, respectively. The shear sense in these samples points to top-to-the-SW to SSW shear. One sample of the upper part, yielding a higher calcite amount, is later overprinted by bulging and displays top-to-the-NNE shear. We postulate to differentiate two main deformation steps. The first is the overall present subgrain rotation and grain boundary migration recrystallization combined to top ~SW shear is related to the sole accretion to the ophiolite and the eventually following thrusting onto the Arabian Plate. The second is correlated to a post-obduction extensional top-to-the-NNE shearing, which is associated with tectonic thinning of the ophiolite and mainly documented in the underlying autochthonous units.

scholarly journals The Effects of Strain Annealing on Grain Boundary Distribution and Hardening in Superpure Nickel

1996 ◽  
Vol 28 (1-2) ◽  
pp. 71-79 ◽  
Author(s):  
C. B. Thomson ◽  
V. Randle
Keyword(s):  
Grain Boundary ◽  
Electron Backscatter Diffraction ◽  
Pure Nickel ◽  
Special Boundary ◽  
Special Boundaries ◽  
Commercially Pure ◽  
Electron Backscatter ◽  
Twin Formation ◽  
High Level ◽  
Backscatter Diffraction

Electron backscatter diffraction is applied to the study of texture and mesotexture in superpure nickel. Low level strain annealing is shown to influence the grain boundary population such that greater proportions of special boundaries exist. It is found that variations in the texture of a specimen are not reflected by characteristic changes in the grain boundary population, indicating that texture analysis cannot be applied to the prediction of special boundary densities. Mechanisms active during the evolution of special boundaries are discussed and compared to those involved under similar conditions in commercially pure nickel. It is shown that alnnealing twin formation need not be prevalent for a high level of special boundaries to form. Differences in the hardness of various boundary types are identified, such that low angle boundaries and ∑3 boundaries close to exact misorientation can be categorized separately to other boundaries, in that they show minimal hardening.

Static Recrystallization of Magnesium Alloy during TRC-HC Deformation Followed by Annealing

2011 ◽  
Vol 295-297 ◽  
pp. 730-733 ◽  
Author(s):  
Yong Wang ◽  
Shou Ren Wang ◽  
Ru Ma ◽  
Li Ying Yang
Keyword(s):  
Magnesium Alloy ◽  
Grain Boundary ◽  
Static Recrystallization ◽  
Electron Backscatter Diffraction ◽  
Boundary Migration ◽  
Transmission Electron ◽  
Subgrain Rotation ◽  
Twin Roll Cast ◽  
Backscatter Diffraction ◽  
Twin Roll

Using optical microscopy, electron backscatter diffraction and transmission electron microscopy, the static recrystallization (SRX) mechanisms of ZK 60 magnesium alloy was examined under twin-roll-cast and hot compression (TRC-HC, 350 °C/0.1 s-1) and subsequent annealing (1000 second at 250-400°C). The static recrystallization (SRX) mechanisms, such as grain boundary migration (GBM), grain boundary bulging (GLB) and subgrain rotation (SGR), were discussed.

A Grain Boundary Engineering Approach to Promote Special Boundaries in a Pb-base Alloy

2002 ◽  
Vol 730 ◽  
Author(s):  
D.S. Lee ◽  
H.S. Ryoo ◽  
S.K. Hwang
Keyword(s):  
Grain Boundary ◽  
Thermomechanical Processing ◽  
Base Alloy ◽  
Coincidence Site Lattice ◽  
Grain Boundary Engineering ◽  
Site Lattice ◽  
Special Boundaries ◽  
Engineering Approach ◽  
Electrochemical Evaluation ◽  
Battery Application

AbstractA grain boundary engineering approach was employed to improve the microstructure of a commercial Pb-base alloy for better performance in automobile battery application. Through a combination of cold working, recrystallization and subsequent thermomechanical-processing, it was possible to increase the fraction of the low ∑ coincidence site lattice boundaries up to 91% in addition to the substantial grain refinement. A preliminary electrochemical evaluation indicated a better corrosion resistance in the experimental material laden with the special boundaries. The high frequency of the coincidence site lattice boundaries in the specimens was interpreted in terms of the '∑3 regeneration' model proposed in previous works.

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